Ink jet printing systems are known in which a print head defines one or more rows of orifices which receive an electrically conductive recording fluid, such as for instance a water base ink, from a pressurized fluid supply manifold and eject the fluid in rows of parallel streams. Printers using such print heads accomplish graphic reproduction by selectively charging and deflecting the drops in each of the streams and depositing at least some of the drops on a print receiving medium, while others of the drops strike a drop catcher device.
An existing assembly method for assembling the components of an ink jet print head includes locating the droplet generator with the aid of an assembly fixture, then using an epoxy or other adhesive to fasten it into place. The charge plate/catcher assembly was then aligned to the droplet generator through the use of external adjustment fixtures. Once a proper alignment was achieved, the charge plate/catcher assembly was fastened with screws to the common frame holding the droplet generator.
Unfortunately, use of epoxy in existing assembly and alignment methods has had some drawbacks. For instance, the use of adhesive increases assembly cycle time, since it takes several hours for the adhesive to cure. The use of epoxy is also problematic in that epoxy is temperature and humidity sensitive. Finally, the sensitivity of the alignment is such that the final fastening of charge plate/catcher assembly once alignment is achieved can and does alter the alignment, requiring a realignment.
In order to overcome the problems associated with using an epoxy, a mechanical structure for mounting and aligning components of an ink jet printer is disclosed in co-pending, commonly assigned U.S. patent application Ser. No. 860,483. The co-pending application provides a means for mounting and aligning the drop charging and deflected drop collector and the droplet generator of an ink jet print head, within a frame structure for holding the two components. The precise positioning of the alignment is achieved by incorporating three degrees of freedom of adjustment into the frame which are self-locking. Unfortunately, the location of screws for in/out adjustment is located behind the resonator, which is extremely difficult for the operator during the adjustment operation. Since the z height adjustment controls the filament length breakoff location relative to the charging leads, lack of assembly consistency in the location of the charge plate relative to the catcher mounting surface requires matching resonators to charge plates, instead of having a universal setting. Finally, scaling up from the flex assembly would create a print head of excessive size.
It is seen then that there is a need for an apparatus for mounting and alignment components of an ink jet print head which overcomes the problems associated with existing techniques.